The fabrication of useful nanoscale devices has proved difficult. Approaches based on porous aluminum oxide (Anopore™), ion-track-etched polycarbonate (Nuclepore™), ion-track-etched mica, and other approaches, have been attempted. Examples of these are disclosed by Mitchell et al., in “Template-Synthesized Nanomaterials in Electrochemistry”, Electroanalytical Chemistry, A. J. Bard and I. Rubinstein, Eds., 21, (1999), 1–74; Strijkers et al., in “Structure and Magnetization of Arrays of Electrodeposited Co Wires in Anodic Alumina,” J. App. Phys., 86, (1999), 5141; Han et al., in “Preparation of Noble Metal Nanowires Using Hexagonal Mesoporous Silica SBA-15,” Chem. Mater., 12, (2000), 2068–2069; Whitney et al., in “Fabrication and Magnetic Properties of Arrays of Metallic Nanowires,” Science, 261, (1993), 1316; and in U.S. Pat. No. 6,185,961 for “Nanopost arrays and process for making same,” to Tonucci et al.; and U.S. Pat. No. 6,187,165 for “Arrays of semi-metallic bismuth nanowires and fabrication techniques therefor,” to Chien et al. These approaches result in materials which can be very difficult or impossible to pattern laterally and/or integrate. Other devices which can be prepared are macroscopic in scale, as disclosed in U.S. Pat. No. 6,187,164 for a “Method for creating and testing a combinatorial array employing individually addressable electrodes,” to Warren et al.
Recently, companies such as Samsung and Hitachi have used carbon nanotubes as field emission sources to make prototype field emission (FE) displays. FE devices based on carbon nanotube materials are disclosed in “Flat panel display prototype using gated carbon nanotube field emitters,” by Wang et al., App. Phys. Lett., 78, (2001) 1294, and can provide acceptable field emission, but can be difficult to fabricate.
Serial writing processes can be used to pattern magnetic media, as disclosed in “Writing and reading perpendicular magnetic recording media patterned by a focused ion beam,” by Lohau et al., App. Phys. Lett., 78, (2001), 990, and “Magnetic block array for patterned magnetic media” by Koike, et al., App. Phys. Lett., 78, (2001), 784. Researchers at IBM Almaden Research Center have utilized a fabrication scheme that resulted in patterned media having storage density of 100 Gb/in2, as described in Lohau et al. This scheme used a focused Ga+ ion beam to cut trenches in granular Co70Cr18Pt12 film media. These processes tend to be slow, and are not well suited to high throughput manufacture.
The efficiency of thermoelectric (TE) cooling devices has not increased significantly during the last 40 years, and currently, the figure-of-merit (ZT) of the best materials is less than one. Semimetal materials such as Bi and Bi2Te3 have the highest ZT values and are currently used in commercial TE devices manufactured by companies such as Marlow and Melcor.